M1 RNA, the RNA Subunit of Escherichia coli Ribonuclease P, Can Undergo a pH-Sensitive Conformational Change

After purification from extracts of whole cells. Ml RNA, the catalytic subunit of ribonuclease P from Escherichia coli, apparently must undergo a change in conformation before it can function catalytically. The rate of this conformational change is dependent upon the duration of incubation at various temperatures and pH. ΔE^* of the transition at pH 7.5 is approximately 36 kcal/mol. The change in conformation is not sensitive to Mg²⁺ concentration between 10 and 100 mM. A decrease in A₂₆₀ of Ml RNA in solution has been observed during the incubation period that potentiates the conformational change at 30 °C, but no direct correlation can yet be made to specific structural rearrangements.